This has been an issue for quite some time now, finally found time to search for a solution and couldn't find one

If I render a scene in 3dsMAX and save it as a PNG file, then I import it to AE, AE doesn't ask what type of alpha is in the image - it always assumes it's straight which is wrong because it's always premultiplied (coming from 3ds MAX at least).

It asks with tiffs, tga, jpeg2000 but NOT with pngs

Any thoughts on that?

If you want to check yourself, maybe on a different 3D software:

- create a plane

- give it a self illuminating red material (so that there is no shading whatsoever)

- throw a black and white gradient to the transparency slot

In AE if you import correctly, on the transparency grid, you'll get a plane of constant red color gradually fading out. If it seems that the more transparent the plane gets, the darker/brighter the red also gets - you have a wrong alpha interpretation.

It sounds as if the default alpha interpretation is set to Straight in AE Preferences. I'm not in front of my AE machine at the moment to double-check, but I'm pretty sure it's in AE Preferences. If it isn't there, check the Interpret Footage settings. Either way, it's a pretty straightforward change.

I never render anything premultiplied from any 3D app. You don't get as good an edge and unless you are specifically using a colored background as a target it makes not sense in a production environment to be using premultiplied alphas. All NLE's default to straight and in almost every case, you get a much better edge.

That said, Dave's right, it's a preferences setting. I have not checked png's or png sequences so I don't know if my machine would show this problem, but then again, I never intentionally produce a premultiplied alpha.